Added SILO example.

silo_example/silo.c

+/* SILO is a scientific database library that can be found at the address
+ *
+ *    https://wci.llnl.gov/simulation/computer-codes/silo
+ *
+ * SILO works together with the scientific visualization code VisIt that
+ * can be found at the address
+ *
+ *    https://wci.llnl.gov/simulation/computer-codes/visit
+ *
+ * Step 1: Installing SILO
+ *
+ * SILO is generally found in the package collection of your distribution.
+ * On Debian for example you can install it via
+ *
+ *   apt install libsilo-dev libsiloh5-0
+ *
+ * If you are on OSX and use homebrew, try
+ *
+ *   brew tap datafl4sh/code
+ *   brew install datafl4sh/code/silo
+ *
+ * and if it does not work, let me know at datafl4sh@toxicnet.eu or at
+ * matteo.cicuttin@uliege.be.
+ *
+ * If you are on other Unices or on Windows, it is likely that you will need
+ * to compile the library yourself. In that case:
+ *
+ * 1) Get  https://wci.llnl.gov/sites/wci/files/2021-01/silo-4.10.2-bsd.tgz
+ * 2) tar -zxvf silo-4.10.2-bsd.tgz
+ * 3) cd silo-4.10.2-bsd
+ * 4) export SILO_PREFIX=<path where you want to install silo>
+ * 5) ./configure --prefix=$SILO_PREFIX
+ * 6) make && make install
+ *
+ * In order to compile your program and link against the copy of SILO you
+ * have just configured and installed, do
+ *
+ * gcc -I$SILO_PREFIX/include -L$SILO_PREFIX/lib myprogram.c -lsilo
+ *
+ * If you installed SILO from your operating system package manager, there
+ * should be no need to specify -I and -L paths, however there is a chance
+ * that you will get the HDF5-enabled version. In that case, if -lsilo does
+ * not work, try -lsiloh5.
+ *
+ * This program demonstrates SILO usage. Detailed information can be found in
+ * https://wci.llnl.gov/sites/wci/files/2020-08/GettingDataIntoVisIt2.0.0.pdf.
+ *
+ * This program is compiled as described above. When run, it produces a
+ * .silo file that you should be able to open in VisIt:
+ *
+ * 1) Launch VisIt
+ * 2) Open your file using the "Open" function
+ * 3) Add -> Mesh -> mesh
+ * 4) Add -> Pseudocolor -> u
+ *
+ * You should now see the function x*sin(pi*y) plotted. Double-click on
+ * "Pseudocolor - u" in the list of the variables and play with the plot
+ * settings.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <silo.h>
+
+#define DB_FILENAME "silo_test.silo"
+#define DB_MESHNAME "mesh"
+
+#define SIZE_X  16
+#define SIZE_Y  32 
+
+static void *
+Malloc(size_t size)
+{
+    void *ret = malloc(size);
+    if (!ret) {
+        fprintf(stderr, "malloc() failed\n");
+        exit(EXIT_FAILURE);
+    }
+    return ret;
+}
+
+int
+main(int argc, const char *argv[])
+{
+    /* Open a SILO database, see pag. 17 listing 2-3 of the manual. */
+    DBfile *db = DBCreate(DB_FILENAME, DB_CLOBBER, DB_LOCAL,
+        "My first SILO test", DB_PDB);
+    if (!db) {
+        fprintf(stderr, "Could not create DB\n");
+        return 1;
+    }
+
+    /* Write a cartesian mesh, see pag. 21 listing 2-9 of the manual.
+     * If you want to write a 3D mesh, see listing 2-12. */
+    double *x = (double *) Malloc(SIZE_X*sizeof(double));
+    double *y = (double *) Malloc(SIZE_Y*sizeof(double));
+
+    double dx = 1./(SIZE_X-1);
+    for (size_t i = 0; i < SIZE_X; i++)
+        x[i] = i*dx;
+
+    double dy = 1./(SIZE_Y-1);
+    for (size_t i = 0; i < SIZE_Y; i++)
+        y[i] = i*dy;
+
+    int dims[] = {SIZE_X, SIZE_Y};
+    int ndims = 2;
+    double *coords[] = {x, y};
+
+    DBPutQuadmesh(db, DB_MESHNAME, NULL, coords, dims, ndims, DB_DOUBLE,
+        DB_COLLINEAR, NULL);
+
+    /* Write a nodal variable, see section 4.11 of the manual. */
+    double *u = (double *) Malloc(SIZE_X*SIZE_Y*sizeof(double));
+
+    for (size_t i = 0; i < SIZE_Y; i++)
+        for (size_t j = 0; j < SIZE_X; j++)
+            u[SIZE_X*i + j] = sin(i*dy*M_PI)*(j*dx);
+
+    DBPutQuadvar1(db, "u", DB_MESHNAME, u, dims, ndims, NULL, 0, 
+        DB_DOUBLE, DB_NODECENT, NULL);
+
+    free(u);
+    free(y);
+    free(x);
+    DBClose(db);
+    return 0;
+}